Nowadays, almost everyone has a personal computer, laptop, tablet and/or mobile phone. Commonly, these user equipment devices are equipped with hardware for connecting to a computer network, such as a local area network set up at home or at work, also known as a private network. Private networks are usually connected to a wide area network, which is typically a server in the World Wide Web, via a private router, also known as a private gateway, which sends and routes data packets within and between networks.
In general, two main parts can be distinguished in the private gateway architecture: a control plane and a data plane. The control plane contains routing protocols to discover the overall network topology and draw a routing table, which defines what to do with incoming data packets. The data plane forwards data packets based on the routing and forwarding information of the control plane protocols. Together, they route the network traffic between a private network and another network. More specifically, private gateways commonly have a Dynamic Host Configuration Protocol (DHCP) server, which assigns IP addresses to the user equipment devices in the private network, which simplifies the configuration network configuration, and contain a Network Address Translation (NAT) function, which allows connecting multiple devices to the network using only one IP address. In addition, modern private gateways comprise functions for security, logging, network storage, media services, smart home control and often contain a firewall.
Private gateways can be intelligent and complex devices and a wide variety of different models are available on the market. Both this diversity and complexity can make the implementation of new service features difficult (and expensive). Furthermore, service providers tend to reduce their operational and capital expenditure and increase their revenues by offering more services. For service providers, it can be more attractive to virtualize private network services, i.e. to run them elsewhere, for example at a server somewhere in the World Wide Web. Such virtualization has multiple advantages. The locally installed equipment can be much simpler and it allows updating services without locally updating networking equipment. The drawback of moving functionality to the server, however, is that when the private gateway and server gateway get disconnected, the main services are lost as well. Currently, the functionality is located at the private gateway and all services are still available in the private network, even if the connection to the server is down. To prevent loss of services it has been proposed to provide the private gateway with a fall-back connection to the Internet, such as Wi-Fi or GSM (3G/4G) in case the main connection to the Internet, such as by glass fibre or cable, is lost.